[Pw_forum] phonon calculations do not converge

[William Parker]

Hi Iyad,

How strong is the failure to converge at (0, 1/6, 1/6)?  Perhaps a less tight tr2_ph value of, say, 1.0d-10 would get you where you need to be.    

--William 

On Aug 10, 2012, at 12:29 PM, Iyad AL-QASIR wrote:

> Dear PW_Forum,
> 
> I am running phonon calculations for FeSi (a narrow band gap semiconductor) using QE-5.0. I am using a 6x6x6 q-vectors mesh. The first 4 q-points ran successfully and got good phonon values. However when I reach the 5th point(0 1/6 1/6). The self-consistent calculations do not converge. I tried to reduce alpha_mix(1) to 0.3 but still have the same problem.
> 
> Below are my input files:
> 
> &control
>  calculation='scf',
>  restart_mode='from_scratch',
>  title='FeSi',
>  outdir='./',
>  prefix='FeSi',
>  pseudo_dir='./',
> /
> &system
>  ibrav=1,
>  celldm(1)=8.4165,
>  nat=8, ntyp=2,
>  ecutwfc=60.0,
>  ecutrho= 720.0,
> /
> &electrons
>  conv_thr=1.0d-9,
>  mixing_mode='plain',
>  mixing_beta=0.7,
>  diagonalization='david',
> /
> ATOMIC_SPECIES
> Fe 55.847 Fe.pw91-sp-van_ak.UPF
> Si 28.086 Si.pw91-n_van.UPF
> ATOMIC_POSITIONS
> Fe 0.134855265   0.134855265   0.134855265
> Fe 0.634855265   0.365144735   0.865144735
> Fe 0.865144735   0.634855265   0.365144735
> Fe 0.365144735   0.865144735   0.634855265
> Si 0.839976366   0.839976366   0.839976366
> Si 0.339976366   0.660023634   0.160023634
> Si 0.160023634   0.339976366   0.660023634
> Si 0.660023634   0.160023634   0.339976366
> K_POINTS {automatic}
> 10 10 10  0 0 0
> ***********************************
> phonons of FeSi
>  &inputph
>   tr2_ph=1.0d-14,
>   prefix='FeSi',
>   amass(1)=55.847,
>   amass(2)=28.086,
>   outdir='./'
>   fildyn='FeSi.dyn',
>   trans=.true.,
>   ldisp=.true.,
>   nq1=6, nq2=6, nq3=6
>   recover=.true.,
>   alpha_mix(1)=0.30
> 
> Any comments and suggestions are welcomed.
> 
> Thanks
> IYAD
> 
> 
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*********************************************************
  William D. Parker                 phone: (630) 252-4834
  Computational Postdoctoral Fellow   fax: (630) 252-4798
  MSD-212, Rm. C-215
  Argonne National Laboratory
  9700 S. Cass Ave.
  Argonne, IL 60439
*********************************************************